How does a Breath Analyser work?
A Breath Analyser estimates your BrAC (breath alcohol content) by measuring the amount of Ethanol in your breath. The first breath analysers were invented in the early 20th century. They were in regular use by Police from the 1940’s. The only other methods for testing for drunkenness at the time were blood or urine tests. These were impossible for police to use out in the field. Breath analysers gave them the system they needed to keep drunk drivers off the road.
How the Body Absorbs Alcohol
When you drink alcohol, the ethanol it contains is absorbed into your body. This is through your mouth, esophagus, stomach, and intestines. Ethanol evaporates easily within the body into your blood stream due to our internal body temperature. As the blood containing this alcohol passes around your lungs, the ethanol evaporates into them. The ethanol is stored in areas in the lungs called alveoli. This can be picked up in your breath by a breath analyser.
The alcohol in your alveoli is related to a BAC (blood alcohol content) ratio of 2100 to 1. This means that 1 ml of blood has around the same amount of alcohol as 2100 mls of air from your lungs. Breath analysers use this ratio to measure your BAC.
Passive and Active Breath Analyser
There are two types of breath analysers available today. These are Passive or Active breathalysers. Passive breathalysers do not give a BAC estimate, they simply show whether alcohol is present in someone’s system. A Passive breath analyser only needs the subject to speak or blow over the device to sample the breath.For example, the subject may be asked to count to ten. These are useful for workplaces that may have a zero-alcohol policy. Any alcohol on the breath will be picked up.
Passive breathalysers can also be useful in situations where a large number of people need to be tested. For example, all staff are tested through a Passive breathaslyser. Only those that test positive to alcohol are tested with the Active breathalyser. As Passive breathalysers are much faster to use, it speeds up this process for a large group.
Police will also use a Passive breathalyser first to speed up roadside breath tests. Only if you fail this Passive test will they put a mouthpiece into the device and do an Active breath test.
Active breath analysers will give an actual estimate of the amount of alcohol in the blood. An Active breath analyser requires the subject to blow into the device through a mouthpiece for a required amount of time. Active breathalysers are much more accurate then Passive. The air analysed by a passive device can be contaminated by fumes, smoke, or dust, . An active device sample is less likely to be contaminated because of the mouthpiece.
Active breathalysers are more common for personal breathalyser use. There are three main types:
Semi-conductor Breath Analyser
Semi-conductor Breath analysers are the most economical type. They are also generally more compact. Some can be small keyrings or similar. The ethyl alcohol in the breath generates an electric current . This occurs as it passes through a mix of acetic acid and water. The electric current formed is in proportion to the amount of alcohol in a person’s blood.
Semi-conductor breathalysers are less accurate than other types however. This is because of the influence of other substances that can act like acetic acid. Diabetics and people on a low-carb diet naturally have more of this in their breath and this can affect the reading on a semi-conductor breathalyser. They are also less accurate over multiple consecutive readings than fuel cell models.
Nevertheless, if you want a simple reading to show that someone has been drinking then these models are perfect and affordable. If you want accurate results every time, then they will not suit.
Fuel Cell Breathalysers
Fuel Cell breath analysers include two platinum electrodes. An acidified electrolyte substance surrounds these electrodes. The ethyl alcohol in the breath is oxidised by passing betwen the electrodes. This oxidization turns it into acetic acid, protons, and electrons. The electrons produce a measurable current. The more oxidized alcohol present, the stronger the current. A microprocessor measures the BAC.
Fuel Cell breath analysers are the most accurate. There are virtually no contamination issues. The acetic acid in the breath of diabetics also does not affect them. Fuel Cell models are also accurate over multiple consecutive tests. Consequently, they are more reliable than semi-conductor models. Police breathalysers are always fuel cell models.
Infra-red Spectrophotometer technology
You will be taken back to the Police station for further tests if you fail a roadside breath test. A desktop breath analyser will be used. These employ Infra-red technology. When you breathe into the analyser, a beam of Infra-red radiation will pass through the sample. The device calculates how much ethanol is in 100ml of air by how much of this radiation reaches the other side of the collection chamber. It uses the same ratio of breath alcohol to blood alcohol as other devices, being 2100:1. The device can then work out the amount of alcohol in the blood and show the results on a screen. These results can be used in Court as evidence.
The Future of the Breath Analyser
Breath Analysers are now a regular feature in many people’s lives. They help keep our roads and workplaces safe and have subsequently saved many lives.
The basic method of breath analysis has not changed much since the first examples. You blow into a device and chemicals within that device react to the alcohol in the breath.
The modern technology now used however has made them much more accurate and reliable. They are also more compact and portable. This technology will no doubt keep improving. Consequently, breathalysers will continue to become a bigger feature in our lives.